1. Field of the Invention
The present invention relates, in general, to power disconnect switches and, specifically, to test switches and, even more specifically, to watthour meter test switches.
2. Description of the Related Art
Power disconnect switches are used in a number of applications, such as watthour meter, relay, instrument transducer and control system calibration, disconnecting, troubleshooting and testing.
In the electric utility application, watthour meters are commonly employed to measure electrical power consumption at a residential or commercial establishment. A cabinet is typically mounted on an outside wall of the residence or building and contains a meter socket having pairs of line and load contacts which are connected to electric power line conductors extending from the utility power network and electric load conductors connected to the residential or building establishment power distribution network. The contacts in the socket receive blade terminals on a plug-in watthour meter to complete an electric circuit through the meter between the line and load terminals in the cabinet for the measurement of electrical power consumption.
Current transformer or CT rated watthour meters and socket adapters are employed in high current applications. In such an application, current transformers are coupled to the line and load conductors and have their output leads connected to terminals in a current transformer or CT rated watthour meter socket adapter. A low current rated watthour meter is then plugged into the socket adapter or socket to measure consumed at the building site.
In addition, potential coils in a watthour meter may also be connected by potential blade terminals to potential blade contacts mounted in the socket or socket adapter and connected by individual conductors to terminals mounted in the terminal portion of the socket adapter.
However, with current transformer rated socket adapters or sockets, it is necessary to short circuit the line and load terminals when the watthour meter is removed from the socket for replacement or testing. Heretofore, test switch devices have been incorporated into the CT rated socket to provide the necessary short circuit or bypass feature.
Exemplary test switches are made by Meter Devices Company, Inc., of Canton, Ohio, the assignee of the present invention. Such test switches are typically mounted in a watthour meter socket immediately below a watthour meter or watthour meter/socket adapter. The test switches are generally in the form of single throw, knife-type switches which are provided in multiples ganged together into one assembly; but each electrically connected between one line contact and one load contact in the socket. Once an optional socket cover is removed, the test switches can be operated as desired to provide the necessary bypass connection between the line and load contacts and conductors prior to removing the watthour meter from the socket for testing, recalibration, replacement, etc.
However, while such test switches have proven to be an effective means for implementing a watthour meter bypass connection, such test switches are not without their drawbacks. Typically, each test switch is formed as a one-piece unit or member, with the electrical contact and terminals mounted on an electrically insulating base. Separate insulating barriers are provided between two adjacent test switches to provide electrical isolation between the connections on two adjacent test switches. Further, such test switches, in one typical mounting arrangement, are secured to a base plate by means of mechanical fasteners, snap-in connections, etc. In another mounting arrangement, apertures are formed in each insulating base and the intervening insulating plates receive elongated, threaded rods to secure the plurality of test switches and insulating plates in a fixed, longitudinal arrangement.
Both mounting arrangements involve many time consuming assembly steps due to the need to separately mount each test switch base to an underlying mounting plate or to align the test switches for receiving the elongated threaded rods there through.
Thus, it would be desirable to provide a test switch apparatus which has a simplified construction for a reduced manufacturing cost. It would also be desirable to provide a test switch apparatus which can be formed of individual identical switch modules re-arrangable in any mounting pattern. It would also be desirable to provide a test switch apparatus having reduced part count.
The present invention is a test switch apparatus which includes a plurality of individually operable switch members, each including a separately actuatable switch or contact capable of opening and closing an electrical circuit between two conductors attached to terminals on the switch member.
In one aspect of the invention, the test switch apparatus includes a plurality of identical modules, each having a base and a planar barrier wall extending from the base. The base has a first sidewall opposed from the barrier wall. Complimentary interconnecting members are formed on the base and the barrier wall for releaseably interconnecting two modules in a side-by-side arrangement. The switch and terminals are mounted on an upper wall of the base between opposed sidewalls.
In one aspect of the invention, the interconnecting members comprise at least one recess formed on one of the sidewalls of the base and the barrier wall and at least one complimentary shaped projection formed on the other of the barrier wall and the first sidewall of the base. In another aspect, two spaced recesses and two spaced mating projections are formed on the barrier wall and the first sidewall of the base.
Lock elements are also optionally formed on each barrier wall and each base for lockingly interconnecting two adjacent switch modules. The lock elements preferably comprise complimentary lock elements formed on the first sidewall of the base and the barrier wall. More preferably, the lock elements interlock after adjacent modules are substantially interconnected by the interconnecting members.
In one aspect of the invention, the lock elements include a projection extending outward from one of the first sidewalls in the base and the barrier wall and a complimentary-shaped recess formed in the other of the barrier wall and the first sidewall of the base.
In another aspect of the invention, at least one end piece is mounted adjacent to an endmost switch module. The end piece includes a planar barrier wall and at least one interconnecting member releasably interconnectible with a mating interconnecting member on the adjacent endmost switch module. The one end piece also includes a base having a first sidewall and an opposed barrier wall with the first portion of the barrier wall contiguous with and extending from the base.
At least one lock projection and one lock receiver are preferably formed on the one end piece and are releaseably interlockable with a complimentary lock projection and lock receiver on the adjacent endmost switch module.
The test switch apparatus of the present invention has significant advantages compared with previously devised test switches, particularly those used in watt-hour meter sockets. The present test switch apparatus is formed of a number of individual, identical switch modules which are rearrangeable in any mounting pattern. This reduces the number of different components required for a typical switch assembly which may incorporate ten or more individual switches. The test switch apparatus of the present invention is also easy to assemble and that it does not require alignment of all the switch modules for the insertion of through rods in aligned bores at opposite ends of all of the switch modules. The interconnecting members and optional lock elements are easily engageable to assemble the test switch apparatus.